Bandgap engineering and toxicity Mitigation in CsPb(BrxCly) mixed-halide perovskite thin films and nanoparticles via Sn2+ substitution

Abstract

Today, materials with the perovskite structure ABX₃ have gained great attention due to their wide applications in energy storage and harvesting. In this work, CsPbBr_xClᵧ nanoparticles were synthesized for potential use in LEDs and solar cells using two different methods. Various halide ratios (Cl: Br = 30:70, 50:50, and 80:20) were dissolved in different solvent mixtures of DMF: DMSO (4:1, 3:2, and 2:3 vol ratio), followed by spin-coating on glass substrates. Among them, the 3:2 solvent ratio showed the most favorable optical and structural properties. To reduce the toxicity of the structure, 5 %, 10 %, and 20 % of SnCl₂ were replaced with PbCl₂ and PbBr₂; however, due to the high sensitivity of Sn²⁺ to oxygen and moisture, photoluminescence properties diminished after coating, which is a limitation for practical applications. To overcome this, a colloidal synthesis was also performed using the ligand-assisted reprecipitation (LARP) method with oleic acid and oleylamine as capping agents, resulting in enhanced environmental stability of the particles. CsPbBr_xClᵧ compositions with the same halide ratios and 5 % SnCl₂ were synthesized via LARP in DMF: DMSO (3:2). The results indicate successful reduction of toxicity while preserving the desired optical and structural characteristics. The samples were analyzed using photoluminescence (PL), UV–vis spectroscopy, FESEM, AFM, and XRD to evaluate their optical properties, surface morphology, and crystallinity.